You need a buffer solution that has pH = 7.00. Which of the following buffer systems should you choose? Explain. (a) H3PO4 and H2PO4 - (b) H2PO4- and HPO42- (c) HPO42- and PO43-

Video transcript

hi everyone for this problem. It reads for a buffer of ph 9.5. Which of the following week, acid conjugate based mixtures, would you choose? Explain your choice. So we have three options here and we need to decide which one we're going to choose and we're dealing with a buffer. Okay, so the selection of an ideal buffer. So we're right here. The selection of an ideal buffer system is going to depend upon the ph of the buffer that we require and the P K A value of the weak acid in the buffer system. So the best buffer or the ideal buffer is the one where the P K a of the weak acid is closest to the required ph value. Okay, so in the problem we're told what the ph value is, we're told that the ph is 9.5. So are ideal buffer is going to be where P K A is equal to P H. Okay, so let's take a look at the weak acids that we have in the problem or in the option choices. Okay, so the first one that we have is acetic acid. The second one that we have is ammonium and the third one that we have is formic acid. And we're going to look up a book appendix or the internet to find the P K values for these three acids. So for acetic acid, the P K A is 4. for ammonia, ammonium. The p K A is equal to 9.25 and four Formic acid. The peak A is equal to 3.74. Okay, so the required ph is 9.5. Okay, so what we want here is a peek a equal to the P. H. So we want the peak A. To equal 9.5. Okay, so the required P. H. Which is closest to the ammonium ion is going to be the best buffer system. Okay? So we can go ahead and choose answer choice B as our correct answer because this is where the peak A equals the P. H. Okay, so the P K. Equals 9.5 which also equals the P. H. So that makes this one the correct choice. That is it for this problem. I hope this was helpful.